Hall Thruster System Design for High Delta-V Missions 高ΔVミッションのためのホールスラスタシステム

Hall Thruster System Design for High Delta-V Missions

高ΔVミッションのためのホールスラスタシステム

Ikkoh Funaki(JAXA), Shigeyasu Iihara(IA) and the Hall Thruster Team 船木一幸(JAXA)，飯原重保(IA)，ホールスラスタチーム

Abstract R&D of a new Hall thruster system for high delta-V missions is now under way at JAXA and IA. The system is designed for so-called all-electric main propulsion of 3 to 6 ton class geostationary satellite as well as for orbital transfer of one-ton class planetary explorer. The system is tentatively targeted at variable thrust (100-400 mN) and Isp (1300-3000s) depending on operational modes. In this paper, R&D status of the Hall thruster system is provided and discussed. 概要 ΔVが3〜6km/sの高ΔVミッションに適合したホールスラスタシステムの研究開発を進めている。同スラスタは、3〜6トン級の全電化衛星、ならびに、1〜2トン級の惑星探査の主推進等幅広いミッションに適合することを目指しており、スラスタ一台あたりの推力は100〜400mN、比推力は動作モードに応じて1300s〜3000s を達成する見通しである。本ペーパーでは、同ホールスラスタの開発状況ならびに想定するサブシステムを紹介する。

1. Introduction 1-kW-class system for deep space maneuvers,1) which Application of electric propulsion (EP) to geostationary suggests ion thrusters are the best solutions for such satellite (Fig.1) or planetary explorer is a cutting edge power levels. However, at a higher power level, hall field where European, USA and Japanese research thrusters are considered more competitive and preferable. organizations and companies are competing against each At power levels below 3 kW, in Japan, R&Ds of hall other. Most matured EP system, ion thruster system, thruster were conducted in universities of Tokyo5), usually shows high performance at a low power level Kyushu3), Gifu4) and so on, and along with these academic from around one-kilowatt up to three-kW, and an example societies, Japanese industry such as Melco5) and IHI6) also is asteroid explorer Hayabusa, which employed conducted some R&D. Recently, in-space propulsion

Impulse ΔV GTO launch Orbit

Earth Earth

GEO (Operational Orbit) Spiral Orbit Raising Maneuver

Fig.1 Application of all electric propulsion system to geostationary satellite: all electric propulsion satellite features high payload ratio against ordinary all-chemical propulsion satellite because most delta-V necessary for GTO to GEO transfer is provided via high-Isp electric propulsion.

workshop at JAXA pursues high power hall thruster (> 10 ratio but the drawback is the long trip time for orbital kW), and basic research is going on for such thrusters as transfer that will take typically half a year. To enable RAIJIN7). Under these circumstances, JAXA, IA, IHI/IA, quick orbital transfer, it is pointed out that hall thruster and Tokyo Metropolitan University (TMU) are doing with a moderate Isp can provide better system, and this is R&D of 3-6 kW class hall thrusters, which are considered the reason western companies such as Aerojet, SMECMA, as the most demanded operational range for a variety of etc. are developing hall thrusters. It depends on selected missions. In this paper, R&D status is provided and Isp, but high thrust to power ratio and low dry weight expected system for the above hall thruster is presented. feature of hall thruster enables quick orbital transfer in less than three months if the optimum Isp is selected. 2. Developing Target of Hall Thruster In short summary, all-EP system seeks for quick orbital All-electric propulsion system refers to a spacecraft transfer from GTO to GEO, which means hall thruster system that two kinds of delta-V, i.e., orbital transfer with higher thrust to power ratio is required. The most delta-V from GTO to GEO and NSSK delta-V, are popular operational range of hall thrusters is an Isp of provided by electric propulsion. The concept of 1,500s to 2000s with a thrust to power ratio of 60 mN/kW, all-electric propulsion system is depicted in Fig.1. This but a thruster with a higher thrust to power ratio with a concept was firstly demonstrated by Boeing, and by lower Isp will deliver spacecraft more quickly and adopting all-EP system, drastic reduction in wet weight of efficiently because higher thrust, hence higher satellite becomes possible, in particular by reducing acceleration, is possible. Vice versa, in NSSK operation, a propellant weight for orbital transfer that will lead to higher Isp of 2,500s to 3,000s is better to suppress drastic reduction in cost per payload; the cost for all-EP propellant consumption for typical GEO satellite lifetime satellite is nearly half of that of conventional chemical of 15-20 years. From the above requirements, it is propulsion based satellite. This is a new business model in summarized that bimodal operation of hall thruster, high the field of commercial satellite. Boeing’s first all-EP thrust mode for quick orbital transfer and high-Isp satellite bus named as 702SP was launched in March 2015, operation for NSSS, is idealistic, and hence enabling such and now it is operated in a geostationary orbit. Ion engine bi-modal operation is the objective of our R&D. Table.1 system’s feature of high-Isp can provide high payload summarized the target along with typically used mode,

Table.1 3-6kW hall thruster target.

BBM1a BBM1b Fig.2 Breadboard model thrusters.

that is designated as ‘intermediate mode’ in the table. characteristics for BBM1a and BBM1b at Xe mass flow rates (6 to 30 mg/s) and discharge voltages of 200 to 3. R&D Status of Hall Thruster Head 800V. As shown in the figures, the maximum thrust was So far, some breadboard models (BBM) targeting at 400 mN, and the maxium Isp was 3,000s, respectively. 3-kW and 6-kW operations were fabricated and tested in Typical operational points of BBM1b are: 1) large thrust laboratory. In this section, two breadboard models, to power ratio, 62 mN/kW at a low Isp of 1,300s, and 2) BBM1a and BBM1b, are described. The effective a higher Isp of 2,350s is obtained at a lower thrust to diameters of the channels are 100 mm for BBM1a and power ratio and at lower power level (3.5 kW) with 140 mm for BBM1b. As shown in Fig.3, Stationary good discharge stability and thermal stability. It is hence Plasma Thruster (SPT) type hall thruster with ceramic found out that a hall thruster with two operational modes channel is adopted. The thruster head design is based on consisting of both high thrust and high Isp mode was numerical prediction, in which not only geometrical and successfully operated in laboratory. magnetic field configuration, but also plasma production and any kinds of loss mechanisms are quantitatively 4. Hall Thruster System Proposals estimated prior to fabrication. 8) The usage of numerical Based on the breadboard results and R&D so far, simulation in preliminary design phase drastically expected system-level specifications are considered and shortens the developing time scale. listed in Table.2 with estimated performance values and Performance tests were conducted in IHI’s vacuum system weight. Three system candidates are considered chamber (2mφ x 3m）and large vacuum chamber at here, including large GEO satellite with all-electric Georgia Institute of Technology (5mφ x 9m). In the propulsion system, and 1000-kg and 2000-kg planetary experiment, the pressure inside the chamber is kept explorer with main propulsion system based on hall below 3x10-5 torr. Figure 4 shows thrust and Isp thrusters.

Fig.3 Thrust and Isp characteristics of breadboard models (BBM1).

Table.2 Hall thruster and its sub-system specification (tentative).

5. Summary and Future Plan References In this study, 3-6 kW class hall thrusters with two 1) H. Kuninaka, K. Nishiyama, I. Funaki, T. Yamada, Y. Shimizu, J. modes (high thrust and high Isp) were demonstrated Kawaguchi, Deep Space Flight of Microwave Discharge Ion Engines onboard HAYABUSA, Journal of Space Technology and with BBM1 thruster heads. Currently, fabrication and Science, Vol.22, No.1, 2006, pp.1-10. T. testing of the next versions of BBM are in progress, and 2) T. Schoenherr, D. Fujita, Y. Ito, P. Bambach, J. Suzuki, R. they are intended for improved performance. Using one Kawashima, H. Koizumi and K. Komurasaki, Performance Evaluation and Probe Measurements of Argon-based High-power of the model, limited lifetime testing will be also Thruster with Anode Layer UT-58, Asian Joint Conference on conducted. Following these, preliminary design is to be Propulsion and Power, AJCPP-2014-145, Jeju, Mar. 2014. fixed to start fabricating engineering model thruster 3) N. Yamamoto, S. Kondo, T. Chikaoka, H. Masui and H. Nakashima, Effects of Magnetic Field Configuration on Thrust Performance in A subsystem that is targeted at demonstration in space Miniature Microwave Discharge Ion Thruster, Journal of Applied mission. This system is o be used for orbital raising and Physics.,102, 123304, 2007 . NSSK for 3 to 6 ton class GEO satellite, and tentative 4) T. Miyasaka, K. Asato, R. Muraki, D. Furuta and K. Kubota, schedule is to develop engineering model in FY2016, Investigation of Side by Side Hall Thruster System, 33rd International Electric Propulsion Conference, IEPC-2013-110, followed by various kinds of testing. From FY2017, Washington, D.C., USA, Oct., 2013. prototype model development will start, so that the 5) T. Ozaki, Y. Inanaga, T. Nakagawa and H. Osuga, Development whole subsystem including power-processing unit Status of 200mN class Xenon Hall Thruster of MELCO, IEPC-2005-064, 29th International Electric Propulsion Conference, becomes available by FY2019. If wide operational range Princeton University, Oct.-Nov., 2005. and long lifetime are both established, the hall thruster 6) S. Cho, H. Watanabe, K. Kubota, S. Iihara, K. Honda, K. Fuchigami, becomes also attractive for deep space mission. We can K. Uematsu and I. Funaki, Parametric Kinetic Simulation of an IHI High Specific Impulse SPT-Type Hall Thruster, 50th develop a 6-kW thruster based on BBM1b, and at low AIAA/ASME/SAE/ASEE Joint Propulsion Conference, power levels below 3 kW, BBM1a seems the case. AIAA-2014-3426, Cleveland, OH, July 2014. Thrusters in both power range should be prepared in a 7) N. Yamamoto, T. Miyasaka, K. Komurasaki, H. Koizumi, T. timely manner so that thrusters can be used either for Schonherr, H. Tahara, H. Takegahara, J. Aoyagi, I. Funaki, H. Watanabe, Y. Ohkawa, A. Kakami, Y. Takao, S. Yokota, T. Ozaki industrial case and planetary and space sciences. and H. Osuga, Developments of Robust Anode-layer Intelligent Thruster for Japan IN-space propulsion system, IEPC-2013-244, Acknowledgements 33rd International Electric Propulsion Conference, Washington, D.C., USA, Oct. 2013. This study is conducted as the joint study of JAXA, IA, 8) S. Cho, H. Watanabe, K. Kubota, S. Iihara, K. Fuchigami, K. IHI and TMU. JAXA’s research and development Uematsu and I. Funaki, Study of Electron Transport in a Hall directorate currently support the study, and the authors Thruster by Axial–radial Fully Kinetic Particle Simulation, Phys. greatly appreciate the efforts and contributions of the Plasmas, Vol.22, 103523, 2015. staffs of the Hall Thruster Team.